WO 2007/069200 A1 discloses in its FIG. 4 a lighting circuit fed via a voltage source and first and second current sources. The lighting circuit comprises blue and green LEDs and red and amber LEDs. Owing to the fact that the blue and green LEDs require a larger current amplitude than the red and amber LEDs, the red LED is coupled serially to the first current source and the amber LED is coupled serially to the second current source and both combinations are coupled in parallel to each other, and the parallel combination is coupled serially to a serial combination of the blue and green LEDS. This way, the red and amber LEDs each draw 350 mA, and the blue and green LEDs each draw 700 mA. Each one of the LEDs is coupled in parallel to a switch for control purposes. The entire combination is coupled to the voltage source.
US 2012/274228 A1 discloses a circuit for driving a LED load and comprises a controllable converter and a control circuit. The control circuit is responsive to a PWM signal, the signal having two levels to turn off respectively turn on the converter. A load disconnect switch is coupled in series with the LED load and is responsive to the PWM signal. The load disconnect switch opens the load current path when the converter turns off, thereby terminating the load current flow.